The overall hypothesis of this project is that radiographic, physiologic, or biologic measures are able to identify interstitial lung disease at an early stage, are able to define the overall activity of the disease, and are able to predict the course of the lung disorder. During the next five years, the investigators intend to continue to evaluate the clinical utility of these biomarkers for assessing interstitial lung disease. The goal of this project is to identify risk factors that determine the activity of disease and prognosis for patients with interstitial lung disease. Although the applicants and other investigators have found associations between a variety of disease measurements, the clinical utility of biomarkers for assessing interstitial lung disease has not been critically evaluated. While Project I is not designed to study the pathogenesis of interstitial lung disease, knowledge of the pathogenesis of these disorders may suggest now biomarkers for these clinical studies. Moreover, findings from the studies proposed in Project I may enhance and re-direct the pathogenic studies outlined in other projects in this SCOR Program. The investigators will study and compare four types of interstitial lung disease - idiopathic pulmonary fibrosis (IPF), asbestosis, interstitial fibrosis associated with rheumatoid arthritis (RA-ILD), and sarcoidosis. Three of these disorders (IPF, asbestosis, and RA-ILD), have a similar radiographic and histologic appearance. In contrast, sarcoidosis exhibits markedly different radiographic and histologic findings. While all of these disorders involve the interstitium of the lung, the anatomic distribution for these diseases, as detected by the high resolution computerized tomography (HRCT) scan, is decidedly different - sarcoidosis primarily involves the airways and peribronchial parenchyma while the other three lung diseases predominantly involve the lung parenchyma. However, in all of these disorders, the high resolution CT (HRCT) scan is able to identify heterogeneous areas of lung involvement. The etiologic factors and prognosis associated with these four diseases are also clearly different. These differences and similarities will allow the evaluation of risk factors and prognosticators both within and across disease categories. The specific aims have been developed to further pursue and extend the ongoing research program in interstitial lung disease at the University of Iowa.